Non-linear adaptive scheme for cancellation of transmit out of band emissions

An apparatus for removing unwanted transmitter emissions from a composite received signal, comprising:

• a first processor for digitally sampling I and Q samples from a modulator;
• a non-linear digital adaptive filter based on a linear combination of selected Volterra kernels through weights derived by mean square error calculations, that receives the I and Q transmitter samples as input signals, and outputs a reproduction of the unwanted transmitter emissions;
• a second processor for selecting a desired portion of the reproduction by frequency shifting and low pass filtering the reproduction, and digitally subtracting the selected desired portion from a composite base band signal;
• and
• a third processor for iteratively adapting the non-linear digital adaptive filter based on a residual error fed back to the non-linear filter to iteratively adapt the weights applied to the non-linear digital adaptive filter.

An apparatus for removing unwanted transmitter emissions from a composite received signal, comprising:

• a first processor for digitally sampling I and Q samples from a modulator;
• a non-linear filter based on a linear combination of selected Volterra kernels through weights derived by mean square error calculations, that receives the I and Q transmitter samples as input signals;
• a second processor for digitally subtracting an output of the non-linear filter from a composite base band signal;
• and
• a third processor for iteratively adapting the non-linear filter based on a residual error fed back to the non-linear filter to iteratively adapt the weights applied to the non-linear filter;
• and a digital frequency shifter and digital low-pass filter inserted at the output of the non-linear filter.

An apparatus for removing unwanted transmitter emissions from a composite received signal, comprising:

• means for digitally extracting I and Q samples from a modulator output;
• means for digitally inputting the I and Q samples to a non-linear digital adaptive filter;
• means for digitally applying weights to the non-linear digital adaptive filter outputs;
• means for digitally combining the non-linear digital adaptive filter outputs to generate a base band reproduction of the unwanted transmitter emissions;
• means for selecting a portion of the reproduction that falls in a desired portion of a receive band by frequency shifting and low pass filtering the reproduction;
• means for digitally subtracting the output of the means for selecting from the composite received signal;
• means for feeding back the residual error;
• means for adapting the non-linear digital adaptive filter iteratively based on the minimization of Mean Square Error power, by iteratively adapting the weights applied to the non-linear digital adaptive filter, wherein the weights are a representation of selected Volterra kernels.

A non-transitory computer-readable medium comprising instructions, which when executed by a processor cause the processor to perform the following operations:

• extract digitally I and Q samples from a modulator output;
• input digitally the I and Q samples to a non-linear digital adaptive filter;
• apply weights digitally to the non-linear digital adaptive filter output;
• combine the non-linear digital adaptive filter outputs digitally to generate a base band reproduction of unwanted transmitter emissions;
• select a portion of the reproduction by frequency shifting and low pass filtering the reproduction;
• subtract digitally the lowpass filtered and frequency shifted reproduction from a composite signal;
• and
• adapt the non-linear digital adaptive filter iteratively, by iteratively adapting the weights applied to the non-linear digital adaptive filter, wherein the weights are a representation of selected Volterra kernels.